A Portland cement clinker containing a little anhydrous calcium sulphoaluminate, a specified mixed material and a proper amount of gypsum are jointly ground into a hydraulic cementing material with early strength and micro-expansibility, referred to as calcium sulphoaluminate-modified Portland cement (S.M.P.), with execution standard JC/T 1099-2009 Calcium Sulphoaluminate-Modified Portland Cement. Chinese patent ZL 03152992.5 and Chinese patent 86103649 both reported a calcium sulphoaluminate-modified Portland cement clinker and a production method thereof. The calcium sulphoaluminate-modified Portland cement (S.M.P.) differs from general Portland cement, has the advantages of high early strength and micro-expansibility by introducing an anhydrous calcium sulphoaluminate mineral with the characteristics of early strength, rapid hardening and micro-expansibility in the mineral composition, and however has the disadvantages that the setting time is too short and difficult to control, the 3d/28d strength increase rate is low and the like.
SO3 participating in hydration reaction in S.M.P. mainly comes from gypsum and C4A3S. If appropriate gypsum is added, not only can the setting time and the micro-expansibility be improved, but also the early strength can be improved, air shrinkage can be reduced, and the corrosion resistance, freezing resistance, impermeability and the like can be improved. However, if excessive gypsum is added, not only is the retarding effect poor, but also ettringite is easily further formed later to produce expansion stress to reduce the cement strength and, in serious cases, even cause poor soundness. Researches show that in order to ensure qualified soundness of S.M.P., the content of SO3 must be controlled to be less than or equal to 6%, and the initial setting time of the S.M.P. at the moment only reaches about 30 min, so the application requirements are difficult to meet. After a certain amount of mixed material, such as slag and fly ash, is added, the setting time can be prolonged, and the initial setting time can be prolonged to about 60 min (adding 30% of fly ash or 30% of slag). (Liu Chen, Wang Xin, Yan Bilan, et al., JC/T Calcium Sulphoaluminate-Modified Portland Cement Industry Standards Introduction [J], cement, 2009, 08:61-64). Thus, in order to meet the technical requirements of application of the S.M.P. for setting time, strength increase and the like, proper technical measures must be adopted to improve the performance of the S.M.P.